Crystals
Tourmaline
Tourmaline supergroup • boron-bearing ring silicates XY3Z6(T6O18)(BO3)3V3W Trigonal • polar and commonly hemimorphic Long striated prisms • rounded-triangular cross sections Mohs 7–7.5 • specific gravity about 2.82–3.32 Strong pleochroism •...
Tourmaline
Tourmaline supergroup • boron-bearing ring silicates XY3Z6(T6O18)(BO3)3V3W Trigonal • polar and commonly hemimorphic Long striated prisms • rounded-triangular cross sections Mohs 7–7.5 • specific gravity about 2.82–3.32 Strong pleochroism •...
Flint
Dark variety of chert Predominantly SiO2 Microcrystalline silica rock Mohs approximately 6.5–7 Conchoidal fracture Nodules and layers in chalk or limestone Produces sparks against high-carbon steel Black, gray, brown, honey,...
Flint
Dark variety of chert Predominantly SiO2 Microcrystalline silica rock Mohs approximately 6.5–7 Conchoidal fracture Nodules and layers in chalk or limestone Produces sparks against high-carbon steel Black, gray, brown, honey,...
Kunzite
Kunzite • pink-to-violet gem variety of spodumene • LiAlSi2O6 Pyroxene group • monoclinic single-chain silicate Strong pleochroism • pale blush to saturated lilac by direction Perfect cleavage in two directions...
Kunzite
Kunzite • pink-to-violet gem variety of spodumene • LiAlSi2O6 Pyroxene group • monoclinic single-chain silicate Strong pleochroism • pale blush to saturated lilac by direction Perfect cleavage in two directions...
Iron tiger eye
Iron Tiger Eye • Tiger Iron • banded lapidary rock composed of chatoyant quartz, iron oxides, and red jasper Golden tiger-eye bands • aligned fibrous texture and moving reflected light...
Iron tiger eye
Iron Tiger Eye • Tiger Iron • banded lapidary rock composed of chatoyant quartz, iron oxides, and red jasper Golden tiger-eye bands • aligned fibrous texture and moving reflected light...
Feldspar
Feldspar group • framework silicates that dominate many igneous, metamorphic, and sedimentary rocks Major branches: alkali feldspar and plagioclase Principal endmembers: KAlSi3O8, NaAlSi3O8, and CaAl2Si2O8 Mohs 6–6.5 • two cleavages...
Feldspar
Feldspar group • framework silicates that dominate many igneous, metamorphic, and sedimentary rocks Major branches: alkali feldspar and plagioclase Principal endmembers: KAlSi3O8, NaAlSi3O8, and CaAl2Si2O8 Mohs 6–6.5 • two cleavages...
Dinosaur bone
Dinosaur bone • fossil vertebrate tissue preserved through mineral infilling, replacement, or both Body fossil rather than one mineral species Lapidary gembone is commonly silica-rich Iron and manganese create much...
Dinosaur bone
Dinosaur bone • fossil vertebrate tissue preserved through mineral infilling, replacement, or both Body fossil rather than one mineral species Lapidary gembone is commonly silica-rich Iron and manganese create much...